Recovery boiler

A recovery boiler is used in a kraft processpulp mill to recover the alkaline pulping chemicals from black liquor, which contains lignin from previously processed wood, so that they can be converted to white liquor for reuse. The black liquor is burned, generating heat, which is usually used in the process of making electricity, much as in a conventional steam power plant. The invention of the recovery boiler by G.H. Tomlinson in the early 1930s was a milestone in the advancement of the kraft process.

Recovery boilers are also used in the (less common) sulfite process of wood pulping; this article deals only with recovery boiler use in the kraft process.